In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.
Typically, these pattern miniaturization techniques involve shortening the wavelength (and increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers (wavelength: 248 nm) and ArF excimer lasers (wavelength: 193 nm) are starting to be introduced in the mass production of semiconductor elements. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a shorter wavelength (and a higher energy level) than these excimer lasers, such as electron beam (EB), extreme ultraviolet radiation (EUV), and X-ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material that satisfies these conditions, a chemically amplified composition is used, which includes a base material component that exhibits changed solubility in a developing solution under the action of acid and an acid generator component that generates acid upon exposure.
For example, in the case where the developing solution is an alkali developing solution (namely, an alkali developing process), a positive-type chemically amplified resist composition containing a resin component (base resin) which exhibits increased solubility in an alkali developing solution under the action of acid, and an acid generator component is typically used. If the resist film formed using this resist composition is selectively exposed during formation of a resist pattern, then within the exposed portions, acid is generated from the acid generator component, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution. The unexposed portions remain as a pattern, resulting in the formation of a positive-type pattern. The base resin uses a resin for which the polarity increases under the action of acid, resulting in an increase in the solubility of the resin in an alkali developing solution, but a decrease in the solubility of the resin within organic solvents. Accordingly, if a process that uses a developing solution containing an organic solvent (an organic developing solution) is employed (hereinafter also referred to as a solvent developing process or negative-type developing process) instead of the alkali developing process, then within the exposed portions of the resist film, the solubility in the organic developing solution decreases relatively, meaning that during the solvent developing process, the unexposed portions of the resist film are dissolved in the organic developing solution and removed, whereas the exposed portions remain as a pattern, resulting in the formation of a negative-type pattern. Patent Document 1 proposes a negative-type developing process.
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are widely used as base resins for resist compositions that use ArF excimer laser lithography or the like, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 2).
In recent years, as the demand for high-resolution resist patterns of 0.15 microns or finer has grown, improvements are required not only in the types of lithography properties described above, but also in the level of defects (surface defects) generated following developing. These defects refer to general anomalies within a resist film that are detected when the developed resist pattern is observed from directly above using a surface defect detection apparatus (product name: “KLA”) manufactured by KLA-Tencor Corporation. Examples of these anomalies include post-developing scum, foam, dust, and bridges that link different portions of the resist pattern.
In recent years, in the production of semiconductor elements, liquid crystal display elements and MEMS (Micro Electro Mechanical Systems) and the like, an impurity diffusion layer is frequently formed on the surface of the support. The formation of an impurity diffusion layer typically includes the two stages of impurity introduction and diffusion, and one example of a method of introducing the impurity is an ion implantation process in which an impurity such as phosphorus or boron is ionized within a vacuum, and the ions are then accelerated by a strong electric field and driven into the surface of the support.
A resist pattern formed on a support using a chemically amplified resist composition is widely used as a mask during etching of the support (substrate). Recently, resist patterns have also started to be used, within the aforementioned ion implantation process, as a mask that enables the impurity ions to be driven selectively into the implantation support surface.
As a composition for use within an ion implantation process, a radiation-sensitive resin composition for ion implantation has been disclosed that includes a (meth)acrylate ester resin containing an acid-dissociable group which becomes alkali-soluble upon dissociation of the acid-dissociable group, an acid generator, and a phenyl group-containing low molecular weight compound that generates no new acid upon exposure to radiation (see Patent Document 3).